diff --git a/init.zsh b/init.zsh
index 9b466450..d663b572 100644
--- a/init.zsh
+++ b/init.zsh
@@ -7,10 +7,9 @@
 #
 
 # Check for the minimum supported version.
-min_zsh_version='4.3.10'
+min_zsh_version='4.2.6'
 if ! autoload -Uz is-at-least || ! is-at-least "$min_zsh_version"; then
   print "omz: old shell detected, minimum required: $min_zsh_version" >&2
-  return 1
 fi
 unset min_zsh_version
 
diff --git a/modules/editor/init.zsh b/modules/editor/init.zsh
index 0fbd5711..bdeb9bdd 100644
--- a/modules/editor/init.zsh
+++ b/modules/editor/init.zsh
@@ -40,6 +40,13 @@
 #     zstyle ':omz:module:editor' completing '...'
 #
 
+# Check for the minimum supported version.
+min_zsh_version='4.3.10'
+if ! autoload -Uz is-at-least || ! is-at-least "$min_zsh_version"; then
+  return 1
+fi
+unset min_zsh_version
+
 # Dumb terminals lack support.
 if [[ "$TERM" == 'dumb' ]]; then
   return 1
diff --git a/modules/git/init.zsh b/modules/git/init.zsh
index e3c3ac84..cf15851e 100644
--- a/modules/git/init.zsh
+++ b/modules/git/init.zsh
@@ -5,6 +5,10 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+if (( ! $+commands[git] )); then
+  return 1
+fi
+
 # Source module files.
 source "${0:h}/alias.zsh"
 source "${0:h}/hub.zsh"
diff --git a/modules/history-substring-search/init.zsh b/modules/history-substring-search/init.zsh
index a0ff287f..66fc0349 100644
--- a/modules/history-substring-search/init.zsh
+++ b/modules/history-substring-search/init.zsh
@@ -6,6 +6,13 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Check for the minimum supported version.
+min_zsh_version='4.3.10'
+if ! autoload -Uz is-at-least || ! is-at-least "$min_zsh_version"; then
+  return 1
+fi
+unset min_zsh_version
+
 source "${0:h}/external/zsh-history-substring-search.zsh"
 
 if zstyle -t ':omz:module:history-substring-search' case-sensitive; then
diff --git a/modules/rsync/init.zsh b/modules/rsync/init.zsh
index e0f866a8..2117e20e 100644
--- a/modules/rsync/init.zsh
+++ b/modules/rsync/init.zsh
@@ -5,6 +5,10 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+if (( ! $+commands[rsync] )); then
+  return 1
+fi
+
 # Aliases
 _rsync_cmd='rsync --verbose --progress --human-readable --compress --archive --hard-links --one-file-system'
 
diff --git a/modules/screen/init.zsh b/modules/screen/init.zsh
index 8c0f1d57..f1275495 100644
--- a/modules/screen/init.zsh
+++ b/modules/screen/init.zsh
@@ -5,6 +5,10 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+if (( ! $+commands[screen] )); then
+  return 1
+fi
+
 # Aliases
 alias sl="screen -list"
 alias sn="screen -U -S"
diff --git a/modules/syntax-highlighting/init.zsh b/modules/syntax-highlighting/init.zsh
index 88ec7b47..297955db 100644
--- a/modules/syntax-highlighting/init.zsh
+++ b/modules/syntax-highlighting/init.zsh
@@ -5,6 +5,13 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Check for the minimum supported version.
+min_zsh_version='4.3.10'
+if ! autoload -Uz is-at-least || ! is-at-least "$min_zsh_version"; then
+  return 1
+fi
+unset min_zsh_version
+
 if zstyle -t ':omz:module:syntax-highlighting' color; then
   source "${0:h}/external/zsh-syntax-highlighting.zsh"
 
diff --git a/modules/terminal/init.zsh b/modules/terminal/init.zsh
index d0bab0b7..b27e9b2b 100644
--- a/modules/terminal/init.zsh
+++ b/modules/terminal/init.zsh
@@ -6,6 +6,13 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Check for the minimum supported version.
+min_zsh_version='4.3.10'
+if ! autoload -Uz is-at-least || ! is-at-least "$min_zsh_version"; then
+  return 1
+fi
+unset min_zsh_version
+
 # Dumb terminals lack support.
 if [[ "$TERM" == 'dumb' ]]; then
   return 1
diff --git a/modules/tmux/init.zsh b/modules/tmux/init.zsh
index c066ea98..7d3b266e 100644
--- a/modules/tmux/init.zsh
+++ b/modules/tmux/init.zsh
@@ -6,6 +6,10 @@
 #   Colin Hebert <hebert.colin@gmail.com>
 #
 
+if (( ! $+commands[tmux] )); then
+  return 1
+fi
+
 # Aliases
 alias ta="tmux attach-session"
 alias tl="tmux list-sessions"
diff --git a/modules/utility/init.zsh b/modules/utility/init.zsh
index 53b618d4..2e58c8e0 100644
--- a/modules/utility/init.zsh
+++ b/modules/utility/init.zsh
@@ -56,7 +56,9 @@ alias type='type -a'
 # ls
 if is-callable 'dircolors'; then
   # GNU Core Utilities
-  alias ls='ls --group-directories-first'
+  if [[ `dircolors --version |head -1 |awk '{print $NF}'` > 6 ]]; then
+    alias ls='ls --group-directories-first'
+  fi
 
   if zstyle -t ':omz:module:utility:ls' color; then
     if [[ -s "$HOME/.dir_colors" ]]; then